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DS - Number Systems

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Source: — Data Sufficiency |

by simplythebest » Fri Jun 15, 2007 5:32 am
I am Getting the answer as B?

Is it right?
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Re: DS - Number Systems

by bingojohn » Fri Aug 10, 2007 11:42 am
f2001290 wrote:If (y+3)(y-1) – (y-2)(y-1) = r(y-1), what is the value of y?
(1) r^2 = 25
(2) r = 5
The question must be wrong.

.... (y+3)(y-1) – (y-2)(y-1) = r(y-1)
=> (y-1) {(y+3)-(y-2)} = r(y-1)
=> y+3-y+2 = r
=> 5 = r

the value of y cannot be determined. Answer [E].

The title/subject of this topic is meaningless. This problem has nothing to do with number systems.
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Re: DS - Number Systems

by gviren » Mon Aug 13, 2007 9:16 am
bingojohn - On the step 2, you cannot divide the eqn with (y-1) as it is not stated that y!=1

I think the answer is A
=> (y-1) {(y+3)-(y-2)} = r(y-1)
=> 5 (y-1) = r(y-1)
=> r=25 => r=5 or -5
=> With r=5, this equn is insovable
=> When r=-5, 5(y-1) = -5(y-1)
=> y-1=-y+1
=> y=1

Let me know if anyone has different opinion
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Re: DS - Number Systems

by bingojohn » Mon Aug 13, 2007 12:53 pm
gviren wrote:bingojohn - On the step 2, you cannot divide the eqn with (y-1) as it is not stated that y!=1

I think the answer is A
=> (y-1) {(y+3)-(y-2)} = r(y-1)
=> 5 (y-1) = r(y-1)
=> r=25 => r=5 or -5
=> With r=5, this equn is insovable
=> When r=-5, 5(y-1) = -5(y-1)
=> y-1=-y+1
=> y=1

Let me know if anyone has different opinion
Oops, my ignorance. Thanks for pointing that out.

However, statement (1) is not giving us any more information than is already presented in the question itself... how is the answer [A]?

It should still be [E], because we don't know for sure if r = -5.
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Re: DS - Number Systems

by Auzbee » Sun Aug 19, 2007 4:23 pm
[quote="gviren"]
I think the answer is A
=> (y-1) {(y+3)-(y-2)} = r(y-1)
=> 5 (y-1) = r(y-1)
=> r=25 => r=5 or -5
....
[/quote]

We still cannot determine from the i statement if r =5 or -5. I think the answer is E.
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by krishnamurthyu » Mon Aug 20, 2007 8:09 am
Given :
(y+3)(y-1) – (y-2)(y-1) = r(y-1)
(y+3)(y-1) – (y-2)(y-1) - r (y-1 ) = 0;
(y-1) [ (y+3)- (y-2) - r ] =0
(y-1) [ y+3 - y + 2 - r ] =0
(y-1) (5-r) =0
i.e y=1 or r =5

y = ?

(1) r^2 = 25
r = (5,-5)
r = 5 : Equation holds good , y=1 maybe may not be true
r =-5 ; Equation doesnt hold good ; y=1 ;

Not Sufficient.

2)r = 5
r = 5 : Equation holds good , y=1 maybe may not be true.
Not Sufficient.

1+2
r = 5 : Equation holds good , y=1 maybe may not be true.
Not Sufficient.
ANS:E
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